Reconstitution is the single highest-leverage skill in research peptide work. Get it right and the rest of the protocol does the work for you. Get it wrong and you just paid for a vial of dead powder. The good news: it's mechanical, repeatable, and takes about 90 seconds once you've done it twice.
This guide gives you the gear list, the math (worked out for you), the 7-step procedure, and the 5 mistakes that ruin a fresh vial. It assumes the lyophilized (freeze-dried) vial arrived in good shape from a vendor with a Certificate of Analysis (COA). If your vial came warm, wet inside, or with a damaged stopper, stop and contact the seller.
What you need on the bench
- The lyophilized peptide vial (10 mg or 20 mg is typical)
- Bac water (bacteriostatic water), 30 mL bottle
- One reconstitution syringe, 3 mL with a 21 gauge needle, just for drawing bac water
- Alcohol wipes
- A clean, flat surface and good light
- A label or marker for the vial (date, concentration, your initials)
The reconstitution syringe is separate from the syringe you use to actually inject. Reuse one syringe for bac water draws across the cycle to save money. Use a fresh insulin syringe (usually 0.5 mL, 29 gauge, 5/16 inch) for every injection.
The dose math (worked out so you don't have to)
This is where most first-timers freeze. The volume of water you add doesn't change how much peptide is in the vial. It changes how much liquid carries each microgram. Pick a volume that gives clean math on your syringe.
Worked examples for a 10 mg vial:
| Bac water added | Concentration | 250 mcg dose | 500 mcg dose |
|---|---|---|---|
| 1 mL | 100 mcg per unit | 2.5 units | 5 units |
| 2 mL | 50 mcg per unit | 5 units | 10 units |
| 3 mL | 33 mcg per unit | 7.5 units | 15 units |
For most research protocols, 2 mL into a 10 mg vial is the sweet spot. The numbers stay clean. The vial fits in the fridge door. You have 28 days to use it before stability starts to drift.
The 7-step procedure
- Wash hands and clean the bench. A wipe of 70% isopropyl alcohol on the work surface is enough. You aren't running a sterile clean room, but you also aren't making a sandwich.
- Wipe both rubber stoppers. Both the bac water vial and the peptide vial. One alcohol wipe each, single pass, let it air dry for 5 to 10 seconds.
- Draw your bac water. Pull the plunger of the 3 mL syringe to your target volume (we'll use 2 mL here). Pierce the bac water stopper. Inject the air into the vial, flip it upside down, and draw 2 mL of water. Tap out any bubbles. Pull the needle out.
- Pierce the peptide stopper at an angle. Insert the needle at about a 45 degree angle with the bevel up, so the water runs down the inside wall of the vial, not straight onto the powder cake.
- Inject slowly. Push the bac water in over 3 to 5 seconds. Slow. You want the water to dissolve the lyophilized cake, not blast it into a fine spray.
- Swirl, don't shake. Hold the vial between thumb and forefinger and roll it gently, or swirl in a small circle. The powder usually goes into solution in 30 to 60 seconds. If there's still residue, give it another minute. Don't shake the vial like a cocktail. Peptide chains can break.
- Label, then refrigerate. Write the date, the concentration, and the peptide name on the vial. Place it upright on the back shelf of the fridge at 2 to 8 degrees C. Most home fridges sit around 4 C, which is ideal. Skip the door for compounds you use less often. The temperature there fluctuates.
The 5 mistakes that ruin a fresh vial
1. Shaking instead of swirling
Mechanical shaking can break the peptide chain and produce visible foam or cloudiness. If your first vial looks frothy, that's the cause. Discard and start over.
2. Injecting water straight onto the powder cake
A direct stream of water onto the cake can fragment the chain. Always angle the needle so the water runs down the wall of the vial first.
3. Wrong water type
If you used sterile water (no preservative), the vial is single-use, period. After 24 hours in the fridge, microbial growth becomes a real risk. For multi-dose vials, use bac water every time. The full breakdown is at /blog/bacteriostatic-water-vs-sterile-water.
4. Letting the vial sit at room temperature for hours
Reconstituted peptides break down faster outside the fridge. A 30-minute draw-and-replace window during your daily dosing is fine. Leaving the vial on the counter overnight is not.
5. Eyeballing the bac water volume
Read the syringe at eye level. The plunger seal has two rings. Read the leading edge of the ring closest to the needle. A 0.1 mL miss changes your effective dose by 5% on a 2 mL reconstitution. Over a 12-week cycle, that compounds.
Storage shorthand
| State | Storage | Window |
|---|---|---|
| Lyophilized, unopened | Freezer, minus 20 C | 2 years |
| Lyophilized, unopened | Refrigerator, 2 to 8 C | 3 to 6 months |
| Reconstituted with bac water | Refrigerator, 2 to 8 C | 28 days (most peptides) |
| Reconstituted with sterile water | Refrigerator, 2 to 8 C | 24 hours (single use) |
The 30-second sanity check before every draw
Pick up the vial, hold it up to a light, and ask three questions. Is the liquid clear or only faintly tinted? Yes. Is anything floating in it or settled on the bottom? No. Is the rubber stopper intact and the cap clean? Yes. If all three answers check, draw your dose. If any answer is no, don't use that vial.
Reconstitution is the part of the protocol you control completely. Spend the 90 seconds, get the math right, label the vial. The rest of the cycle takes care of itself.